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Functions

//Function: check_low //Checks the state of a button/pin and waits for end of button press//Input: // pin: the number of the pin to check//Returns: // 1 if button is pressed/pin is low after waiting for the button to be// released/pin to return to high // 0 if button is not pressed/pin is highint check_low(int pin){ if (is_low(PORT2, pin)){while(is_low(PORT2, pin)){ iolib_delay_ms(1);} return 1;} else return 0;} //Function: stop//Polls the stop pin/button //Returns://1 if button is pressed/pin is low after waiting for the button to be // released/pin to return to high//0 if button is not pressed/pin is high int stop(){return check_low(PIN8); }//Function: play //Updates the 8 output pins with a new value//Input: // out: the 8 bit value to outputvoid play(int out){ if (out and 0x1) pin_high(PORT,PIN0);else pin_low(PORT, PIN0); if ((out and 0x2)>>1) pin_high(PORT,PIN1); else pin_low(PORT, PIN1);if ((out and 0x4)>>2) pin_high(PORT,PIN2); else pin_low(PORT, PIN2);if ((out and 0x8)>>3) pin_high(PORT,PIN3); else pin_low(PORT, PIN3);if ((out and 0x10)>>4) pin_high(PORT,PIN4); else pin_low(PORT, PIN4);if ((out and 0x20)>>5) pin_high(PORT,PIN5); else pin_low(PORT, PIN5);if ((out and 0x40)>>6) pin_high(PORT,PIN6); else pin_low(PORT, PIN6);if ((out and 0x80)>>7) pin_high(PORT,PIN7); else pin_low(PORT, PIN7);} //Function: playSine//Calculates the next value of sine for the given frequency and calls //play//Input: // freq: the frequency of the desired sine wavevoid playSine(int freq){ int t = 0;int out = 0; while(!stop()){out = 128*sin(t++*freq*PI/22050)+128; //calculate the next value to output and incrmemnt discrete time play(out);clock_gettime(CLOCK_REALTIME, and ttime); //get the time ttime.tv_nsec = 0; //clear the nanoseconds but not seconds so that we dont overflow;clock_settime(CLOCK_REALTIME, and ttime); //set the time back clock_gettime(CLOCK_REALTIME, and ttime); //get the time againttime.tv_nsec += 21463; //increment by number of nanoseconds we should wait while(1){ //loop to delay next outputclock_gettime(CLOCK_REALTIME, and curtime); if (curtime.tv_nsec>ttime.tv_nsec) break; }} }//Function: playTriangle //Calculates and outputs the next value of a triangle wave for the given//frequency //Input:// freq: the frequency of the triangle wave void playTriangle(int freq){int out = 0; int t = 0;while(!stop()){ out = (256/(11025/freq))*((11025/freq) - abs(t++ %(2*11025/freq) - (11025/freq))); //calculate next value and increment discrete timeplay(out); clock_gettime(CLOCK_REALTIME, and ttime); //get the timettime.tv_nsec = 0; //clear the nanoseconds but not seconds so that we dont overflow; clock_settime(CLOCK_REALTIME, and ttime); //set the time backclock_gettime(CLOCK_REALTIME, and ttime); //get the time again ttime.tv_nsec += 21463; //increment by number of nanoseconds we should waitwhile(1){ //loop to delay next output clock_gettime(CLOCK_REALTIME, and curtime);if (curtime.tv_nsec>ttime.tv_nsec) break;} }} //Function: playSquare//Updates output to maximum and minimum values at the given frequency to //create a square wave//Input: // freq: the frequency of the square wavevoid playSquare(int freq){ int out = 0;int delay; while(!stop()){out ^= 0xFFFF; //exclusive or all the bits to make a square wave play(out);delay = 1000000000/freq/2; //calculate how long to delay to match frequency clock_gettime(CLOCK_REALTIME, and ttime); //get the timettime.tv_nsec = 0; //clear the nanoseconds but not $ clock_settime(CLOCK_REALTIME, and ttime); //set the time backclock_gettime(CLOCK_REALTIME, and ttime); //get the time again ttime.tv_nsec += delay; //increment by number of nanosec$while(1){ //loop to delay next output clock_gettime(CLOCK_REALTIME, and curtime);if (curtime.tv_nsec>ttime.tv_nsec) break;} }} //Function: playSong0//Outputs a raw 8 bit unsigned audio file as defined above void playSong0(void){char cwd[1024];if (getcwd(cwd, sizeof(cwd))== NULL) perror("getcwd() error"); //Get the current working directory char* path;path = malloc(strlen(cwd) + strlen(SONG0)+2); //Append the defined file name to the path strcpy(path, cwd);char temp[2] = "/";strcat(path, temp); strcat(path, SONG0);FILE *fp; fp = fopen(path, "r");if (fp == 0) perror("error opening file, is the name correct?"); int out = fgetc(fp);while((out != EOF) and and !stop()){ //play each of the stored values until end of file or the stop button is pressed play(out);clock_gettime(CLOCK_REALTIME, and ttime); ttime.tv_nsec = 0;clock_settime(CLOCK_REALTIME, and ttime); clock_gettime(CLOCK_REALTIME, and ttime);ttime.tv_nsec += DELAY; while(1){clock_gettime(CLOCK_REALTIME, and curtime); if (curtime.tv_nsec>ttime.tv_nsec) break;} out = fgetc(fp);} fclose(fp);} //Function: playSong1//Outputs a raw 8 bit unsigned audio file as defined above void playSong1(void){char cwd[1024];if (getcwd(cwd, sizeof(cwd))== NULL) perror("getcwd() error"); char* path;path = malloc(strlen(cwd) + strlen(SONG1)+2); strcpy(path, cwd);char temp[2] = "/";strcat(path, temp); strcat(path, SONG1);FILE *fp; fp = fopen(path, "r");if (fp == 0) perror("error opening file, is the name correct?"); int out = fgetc(fp);while((out != EOF) and and !stop()){ play(out);clock_gettime(CLOCK_REALTIME, and ttime); ttime.tv_nsec = 0;clock_settime(CLOCK_REALTIME, and ttime); clock_gettime(CLOCK_REALTIME, and ttime);ttime.tv_nsec += DELAY; while(1){clock_gettime(CLOCK_REALTIME, and curtime); if (curtime.tv_nsec>ttime.tv_nsec) break;} out = fgetc(fp);} fclose(fp);} //Function: playSong2//Outputs a raw 8 bit unsigned audio file as defined above void playSong2(void){char cwd[1024];if (getcwd(cwd, sizeof(cwd))== NULL) perror("getcwd() error"); char* path;path = malloc(strlen(cwd) + strlen(SONG2)+2); strcpy(path, cwd);char temp[2] = "/";strcat(path, temp); strcat(path, SONG2);FILE *fp; fp = fopen(path, "r");if (fp == 0) perror("error opening file, is the name correct?"); int out = fgetc(fp);while((out != EOF) and and !stop()){ play(out);clock_gettime(CLOCK_REALTIME, and ttime); ttime.tv_nsec = 0;clock_settime(CLOCK_REALTIME, and ttime); clock_gettime(CLOCK_REALTIME, and ttime);ttime.tv_nsec += DELAY; while(1){clock_gettime(CLOCK_REALTIME, and curtime); if (curtime.tv_nsec>ttime.tv_nsec) break;} out = fgetc(fp);} fclose(fp);}

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Source:  OpenStax, Elec 301 projects fall 2014. OpenStax CNX. Jan 09, 2015 Download for free at http://legacy.cnx.org/content/col11734/1.2
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